Sprayable polytetrafluoroethylene aqueous suspensoids containing an organic liquid



Patented Oct. 7, 1952 UNITED S ATES PATENT gorrifce SPRAYABLE POLYTETRAFLUOROETHYLENE AQUEOUS SUSPENSOIDS CONTAINING AN ORGANIC LIQUID Le Verne Kenneth Osdal, Upper Darby, Pa., assignor to du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application January 10, 1950,

Serial No. 137,890

by Kenneth L. Berry, disclose methods of preparing aqueous suspensoids of polyte'trafiuorm ethylene. United States Patent 2,478,299, issued to Kenneth L. Berry, and copending application Serial No. 783,389, filed October 31, 1947, now abandoned, by Carl K. Ikeda, disclose methods of concentrating relatively dilute aqueous sus pensoids oi polytetrafiuoroethylene.

Aqueous suspensoids of polytetrafiuoroethylene are useful, among other things, in forming coatings on various substrates by baking or fusing the polymeric particles of such a suspensoid on the substrate at or above the fusion tempera ture of the polymer (621 F.). However, these aqueous colloidal suspensoids do not behave like ordinary paints, enamels, or lacquers, and, in particular, it has always been difficult to, obtain smooth uniform films therefrom by spraying: In

It is known that adding finely divided pigment to polytetrafiuoroethylene aqueous suspensoids makes them more easily sprayable. However, still further improvement in their sprayability is de sirable, particularly where pigments are objectionable.

The principal object of this invention, therefore, is the production of an aqueous suspensoid of polytetrafiuoroethylene which can be sprayed readily in an ordinary paint spray gun for prolonged periods Without plugging the fluid passages in the gun.

A further object of this invention is the pre paration of an aqueous suspensoid of po1ytetrafiuoroethylene which has the spraying characteristics of ordinary paint, varnish, and lacquer.

These objects are accomplished by emulsifying a premade aqueous suspensoid of substan- ,tially completely polymerized tetrafiuoroethylene -1 with an organic liquid emulsifiable therewith.

' In a preferred embodiment of this invention, a

I premade aqueous suspensoid comprising substanspraying such suspensoids, a normal spray pat tern of air and dispersed droplets occurs during the first few minutes of the operation, but the suspensoid quickly coagulates in the narrow fluid passages of the spray gun and successively re sults in partial plugging of the orifices with. an accompanying spray of irregular blobs of agglomerated polymer particles and, finally, in a complete plugging of the passages with a resultant cessation of the operation. ,This is believed to be directly traceable to the fact that when aqueous suspensoids of polytetrafiuoroethylene are agitated strongly, or are otherwise subjected to rapid motion, such as occurs inspraying, the

minute discrete polymer. particles tend to --ag'- glomerate or coagulate into a plastic mass which separates from the aqueous suspending medium. Besides the inconvenience of thecessation of. the

operation, furthertrouble is encountered in .un plugging the gun, because 1. polyt'etrafiuoro-, v ethylene is not soluble in'the usual solvents,

tially completely polymerized tetrafluoroethylene,

wetting agent, and water is agitated with additional Wetting or emulsifying agent and toluene,

the principal ingredients being present in the final composition in the ratio of parts of polytetrafiuoroethylene -to 487 parts .o'fvwater and 6.3 parts of toluene. This produces a creamy emulsion which is easily and continuously sprayable in a conventional paint spray gun.

,-.,The following examples in which the" parts are by weight, illustraterthe methods and prod-- nets of this inventions/iv v T a A concentrated, polytetrafiuoroethylene aqueous suspensoid produced by; the polymerization of tetrafiuoroethylene i n:,w.ater as describedin the copending applications of Kenneth L, Berry, Serial No= 23,400, filed Apri l-26, .1948, cry-Serial No. 107,137,-filed July-:27, 1949, and modified by the addition of Duponol" ME, had the following composition: H

, 100.0 Duponolt ME is the sodium salt of the sulphuric acid ester of a mixture of long chain alcohols, predominantly lauryl alcohol.

This aqueous suspensoid was emulsified as follows:

Parts This emulsion was sprayed onto a test panel using a conventional paint spray gun (De Vilbiss MBC suction type using an FF tip with a No. 30 cap). The emulsion sprayed easily, produced a 5 smooth, uniform wet coat on the test panel, and Aqueous suspensold of polytetmfluom' 3920 did not plug the gun. When all of the suspensoid iggi g 908 had been sprayed, the fluid passages of the gun i w figf 36 were easily cleaned by rinsing with water. Toluene 320 m Other emulsions of the polytetrafluoroethylene 5 77 aqueous suspensoids were prepared, as in Example 1, and had the compositions shown in the follow- 5261 mg table:'

Table Aqueous Suspcnsoid Addi- Emulsi- Ex. Polytional lying Organic Liquid 11132-1: ponor. Water Water Agent ethylene 14. 07 0.15 9.5 19.5 2.90 36. 2 0. 36 16.3 21. 1 1.30 Ea) 26.4 Toluene (b). 40.4 0.40 18.3 17.7 1.50 a) 23.6Toluene(b). 40.4 0. 40 18.3 23.6 1.5001) 17.7 Toluene (b). 40. 4 0:40 .18. 3' 29. 5 1. 50 (a) 11.8 Toluene (b). 40.4 0.40 15.5 55.4 1.50 (0) 59101115550). 40. 4 0. 40 18.3 55.4 1.50 (a) 2.9 Toluene (b). 42.4 0. 42 21.5 27.5 2.10 (a) 5.5 Pcilydimethylsilox- 8118 C 42. 6 0.43 17.8 19.5 2.00 (a) 20.1 Hydrocarbon (d). 42.5 0. 45 17.5 19.5 2.00 5) 20.1 Benzene (5 6.35 "Freon 113. 44. 5 0. 45 18.6 24. 2 l. (a) {6.35 Perfiuorocarbon Lube Oil (e). 457 0.45 25.7 19.5 1; 5.1 Mineral 011 (g). 45.7 0.45 25.7 19.5 (a .1 Hydrocarbon (h). 45.5 0.45 20.7 27.4 1.30 (a) 5.1 Toluene (b). 47.1 0. 17 50.0 14.1 1.5001 7.9 v.21 a P. Naph- 8- 47.2 0.47 31.0 15.9 5.9 Toluene (b). 47.5 0.47 31.3 15.1 1.00 (k) 5.0 0 51115550). 49.4 0.50 33.8 3.40 (a) 16 8 Hydrocarbon (m) 50. 6 0.51 22. 8 19. 2 1. 50 (a) 7 4 Toluene 50.0 0. 51 22.5 22.9 1.50 (a) 3.7 Toluene (b). 55. 9 0. 56 25.3 10.6 1. 60 (a) 8.2 Toluene (b). 60.0 0.60 39.4 0.6 Toluene (b).

(a) Triton N-100.

(b) 100% aromatic.

(c) (Viscosity 1000 centistokes) (11) paraflins20% naphthenes-% aromatics. (eh-100% halogenated hydrocarbons (B. P. l170-C/l0 mm. Hg).

(I; =-Duponol" ME.

= Cosmetic grade clear mineral oil.

(/2) 75% paraflins-25% naphthenes.

(1) =59% parafiins-33%naphthenes-8% aromatics. (k) Ammonium cleats. I

(m) #119}, permits-17% naphthcnes72% aromatics.

'Per cent Finely divided polytetrafluoroethylene 44.0 Water 47.4 Duponol ME 1.1 Toluene 6.0 "Triton N-100 1.5

All of the compositions in the above table, when sprayed on test panels, sprayed more easily than the unemulsified suspensoid, gave uniform films, and did not plug the spray gun.

EXAMPLE 24 Parts China clay 804 Distilled water 1292 Duponol NEE 8 The above ingredients were ground in a pebble mill to produce a slurry of finely divided pigment in water.

Parts Pigment slurry above 1117 Emulsified suspensoid of Example 1 4135 These ingredients were blended slowly with moderate agitation in a stainless steel vessel. The

resulting product was asmooth emulsified pigmented polytetrafluoroethylene suspensoid having the following position:

. Per cent Finely divided polytetrafiuoroethylene n 34.6 China clay 8.1 Water 50.4 Duponol ME 1.0 Toluene 4 .8 TrltonN-100 r 1.1

EXAMPLE 25 Pigment slurry 'Parts Titanium dioxide white pigment 610 Distilled water 129 Duponol ME 8 1910 Emulsion Parts Pigment slurry above 1117 Emulsified suspensoid of Example l 4135 Final composition v Y Per cent Finely divided polytetrafluoroethylene- 34.6 Titanium dioxide white pigment 6.8 Water 51.8 Duponol" ME 0.9 Toluene 4.8 Triton N100 a 100.0 EXAMPLEZQ Pigment slurry Parts Chromium tetra-hydrate green pigment- 950 Distilled water 1292 Duponol ME 8 2250. Emulsion Parts Pigment slurry above 1117 Emulsified suspensoid ofExample 1 4135 5252 Final composition Per cent Finely divided polytetrafiuoroe'thylene 34.6 Chromium tetrahydrate green pigment 9.0 Water 49.5 Duponol ME 1.0 Toluene 4.8 Triton N-100 1.1

6 EXAMPLE 2'! Pigment slurry Parts Iron oxide red pigment.. 550 Distilled water 1292 Duponol" ME 8 1850 Emulsion.

1 Parts i-igment slurry above 1117 Emulsified suspensoid of Example 1 v4135 5252 Final composition Per cent Finely divided. polytetrafluoroethylene 34.6 Iron oxide red pigment 6.4: Water 52.1 Duponol ,ME 1.0 Toluene 4.8 Triton N-100 1.1

The products of the above three examples were prepared as in Example 24 and were comparable thereto in spraying characteristics.

Organic liquids other than those shown in the examples are operable in this invention. In general, any volatile organic solvent material of the type generally used in the paint industry can be emulsified with polytetrafluoroethylene aqueous suspenscid to produce a sprayable product within the scope of this invention. Or-

I dinarily, such solvents haveboiling points above room temperature and below about 250 0., although the boiling point is not critical and may be at anypoint consistent with the other desirable properties of the product. Other substances with which the polytetrafiuoroethylene suspensoids may be emulsified include the normally liquid parafiln hydrocarbons (e. g., pentane, hexane, heptane, or octane), aromatic hydrocarbons (e. g.,benzene or xylene), cycloaliphatic hydrocarbons (e. g., cyclohexane), low, medium, and high boiling mineral spirits, light mineral oils, halogenated hydrocarbons (e. g., carbon tetrachloride or trichloroethylene), and homogeneous mixtures of these. Water miscible, or partially miscible, organic liquid materials (e. g., ethers, alcohols or ketones) may alsobe added to the polytetrafluoroethylene suspensoids.

Water soluble salts, acids, and bases may be incorporated in the emulsion where they impart desirable properties to the product.

Any aqueous suspensoid of substantially completely polymerized tetrafluoroethylene may be used in the practice of this invention, but the concentrated suspensoids are preferred.

Where pigmented compositions are desired, the ratios can-be varied between 1 and 300 parts of pigment toeach parts of polytetrafiuoroethylene. Any pigment which is substantially insoluble in water and otherwise harmless to the product, and which can be dispersed in a finely divided form in the aqueous suspensoid, may be substituted for the pigments shown in the examples.

As shown in Examples 17 and 23, it is not always necessary to add an emulsifying agent. Furthermore, the particular wetting or emulsifying agents shown in the other examples can be replaced by the same or different amounts of gas-19 other conventional surface active materials designed for water/organic systems. Such other wetting or emulsifying agents include soaps of the higher fatty acids, alkyl aryl sodium sul fonates, sorbitan salts of the-higher acids-and their polyoxyethylene derivatives,salts' of 'the' sulfates of long chain alcohols, and others conveniently listed in Synthetic detergentsup to date, John W. McCutcheon, published in Soap and Sanitary Chemicals, August, September and October, 1949. The amount of such agents whicfi it is desired to use in these compositions will vary with the activity of the agent and the concentration of the agent in its commercially available form. The amount" is critical for each agent only to the extent that it produces the desired emulsifying action-and does notadversely affect the other properties'of the product.

While wide variationsin the amounts of the principal ingredients arepermissible, itis preferred that the organic liquid be present-in an' amount within the range of 05-57%, the poly tetrafiuoroethylene within the range of 5-74%, and the water within the range of 16-94%; all based on the total amount of these three ingredients. Compositions containing 05-57% of organic liquid, 10-70%of polytetrafluoroethylene, and 2560% of water have been shown-in the examples.

I Any conventional paint spraygun is suitable for applying the compositionsof this invention, such as the suction type spray gun describedin' with a No. 704 cap. I

The polytetrafiuoroethylene' aqueous suspensoids of this invention have been found highly useful for spray coating purposes, and the processes of this invention are useful-in applying Example 1, or the pressure type using an tip application is necessary or desirable.

As many widely different embodiments of this invention may be made without'departing from the spirit and scope thereof, itis understood'th'at the invention is not limited to thespecific emsuch suspensoids to various articles where spraybodiments except as defined in the appended ganic liquid is between about 0.5% and 57% of the total water, polytetrafluoroethylene, and organic liquid.

3. The emulsion of claim 1 in which the polytetrafluoroethylene is between about 5 and 74% of the total water, polytetrafluoroethylene, and organic liquid.

4. The emulsion of claim 1 in which the water is between about 16% and 94% of the total water,

polytetrafiuoroethylene, and organic liquid.

5. The emulsion of claim 1 in' which-the or-"- ganic liquid is an aliphatic hydrocarbon.

6. The emulsion of claim 1 in which the or-' ganic liquid is an aromatic hydrocarbon.

7. The emulsion of claim 6 in which the arcmatic hydrocarbon is toluene.

8. The emulsion of claim 1 in which the organic liquid is a polysiloxane.

9. A sprayable emulsioncomprising a premade aqueous suspensoid of colloidal substantially completely polymerized tetrafluoroethylene, an emulsifying agent, and an organic liquid emulsifled; therewith.

.10. A sprayable emulsion comprising a premade aqueous suspensoid of colloidal substantially completely polymerized tetrafiuoroethylene, an emulsifying agent, an organic liquid emulsifedtherewith, and a pigment.

11. The emulsion of claim 10 in which the pigment is present in a ratio of between about 1 and. 300 parts to l00'parts of polytetrafluoroethylene. V

"12. The e'mulsionof claim 10 in'which the pigment is waterinsoluble.

'13. A sprayable emulsion comprising a premade aqueous suspensoid of colloidal substantially completely polymerized tetrafluoroethylene and an organic liquid emulsified therewith, the organic liquid being between about 0.5% and 57%; the polytetrafluoroethylene being between about 10%"and 70%, and the water being between about 25% and 60%, based on the total of these ingredients.

14. The process of producing a sprayable emulsion of a premade aqueous suspensoid of colloidal substantially completely polymerized tetrafiuoroethylene which comprises adding to such a suspensoid an organic liquid emulsifiable with said suspensoid and moderately agitating the mixture to emulsify it.

- .15. The process of claim 14 in which the organic liquid is between about 0.5% and 57% of the total water, polytetrafluoroethylene, and organic liquid. 7 p 4 p p v 16. The processor claim'14 in which the organic liquid is an aliphatic hydrocarbon.

17. The process of claim 14 in which the organic liquid is an aromatic hydrocarbon.

18. The process of claim 17 in which the arcmatic hydrocarbon is toluene.

19. The processof claim 14 in which the orsubstantially completely polymerized tetrafiuoroethylene which comprises adding to such a suspensoid an emulsifying agent, an organic liquid emulsifiable with said suspensoid, and a pigment and moderately agitating the mixture to emulsify it. v

.' LE VERNE KENNETH OSDAL.

REFERENCES CITED The following references are of record in the file of this patent: v

UNITED STATES PATENTS Number 1 Name Date Brubaker Feb. 5, 1946 

1. A SPRAYABLE EMULSION COMPRISING A PREMADE AQUEOUS SUSPENSOID OF COLLOIDAL SUBSTANTIALLY COMPLETELY POLYMERIZED TETRAFLUOROETHYLENE AND AN ORGANIC LIQUID EMULSIFIED THEREWITH. 